Beneficiation of iron ores



Patented Oct. 29, 1946 BENEFICIATION OF IRON ORES Robert Ben Booth, Springdalaand Earl Conrad Herkenhoff, Stamford, Conn.,

assignors to I American Cyanamid Company, New York, N. Y., a corporation of Maine No Drawing. Application April 5, 1943,

. Serial No. 481,906 I This invention relates to the beneficiation of iron ores by froth flotation processes.

Low grade iron ores have presented a very serious beneficiation problem'because the unit value of iron concentrates is not high and flotation procedures in the pasthave not given commercially useful results. Iron ores containing hematite, magnetite, or similar iron minerals can be subjected to frothflotation in the presence of the typical fatty acid collectors used with oxide ores, but, while some beneficiation takes place, the grade obtained and recovery are not sufiiciently high to make the process commercially feasible, v H Ithas been'propose'd to float oxide ores with water-insoluble reactionproducts of sulfuric acid and petroleu hydrocarbons from lubricating oil stock obtainedasa waste product from the refining lubricating oil stock with strong sulfuric acid, oleum, chlorosulfo'nic or other sulfonating agents and referred to in the trade as mahogany soaps. These reagents give somewhat better results than fatty acids, but the results are not commercial, particularly when iro ores are treated. According to the present invention iron ore pulps'are treated with an inorganic acid such as sulfuric acid, phosphoric acid and the like, and the acid-treated pulp can be floated with mahogany soaps, used alone, or dispersed in petroleum hydrocarbons, alcohols, 'or other oily solvents, to give high grades and good recoveries which permit transforming rejected tailings, waste products from washers, and other low grade ores into commercially acceptable concentrates. An outstanding advantage of the concentrates obtained is their generally granular nature which permits easy dewatering, so that concentrates can be shipped to central locations for sintering. The process is also advantageous in that the reagents used are cheap and in normal times'readily obtainable in large quantities.

The mechanism of the present invention is not completely known, and it is not desired to limit it to any particular theory of operation. Within wide limits the nature of the acidic anion does not appear to play a great role. Almost any reasonably well dissociated inorganic acid can be used. In fact, it is not necessary to add a free acid. Certain acid salts such as sodium or potassium bisulfate and sodium chlorosulfonate work as well as sulfuric acid. There is some difference in the action of different acids. This leads us to believe that probably one'factor of the present invention is the action of the acid on the particles of iron ore. It is possible that another factor may be action on stained gangue such as iron-stained quartz.

It is an advantage of the present invention that the amount of inorganic acid to be used is not critical. This does not mean that the-acids 8 Claims. (01. 209166 7 may be used in unlimited quantities. With every acid and everyore the effect generally increases atfirst with the addition of more acid, reaches a maximum, and then may decline when more acid is used. In general, with sulfuric acid, amounts of acid froml to 5'lbs. per ton of flotation feed" constitute the range of best? operation, with an optimum depending on the ore and other conditions of about 2 to 3 lbs. per ton, These figures apply to processes in" which the pulp is condi tion'ed at' high-"solids. Where conditioning at low solidsis employed, such as for example, at flotation pulp density, acceptable results can be obtained, but the amount of "acidrequired is greatly increased-ranging from 5 to 10 lbs. per ton-"of feed. A commercially acceptable product is obtained, but, because of'thebetter results and smaller reagent consumption, it is preferred to condition at highsolids, although the invention is not limited thereto;

The tremendous improvement obtained by means o-fthe present invention is all the more surprising because oxide 'ore flotation in the presence of anionic collectors such asfatty acids frequently proceeds best in a neutral-or slightly alkaline circuit." In fact, the addition'of any considerableamounts of sulfuric acid with a fatty acid collector will-kill the float altogether. Undoubtedly the acid operates in a different manner with the mahogany soaps. The action does not appear to be one due solely to pH of the circuit, although this may be a contributing factor, because when ore pulp is treated with an acid such as sulfuric acid and'then floated in a cir-' cuit in which the pH is raised by'the addition of an alkali, such as sodium carbonate, the improved results of the present invention are still retained.- This is an added reason for believing that at least one factor in the process is some surface effect of the acid on the ore particles. Water-insoluble reaction products of sulfuric acid andpetroleum hydrocarbons from lubrieating oil stock vary duite widely with different crude oils and different refining procedures. The

I compositions are somewhat indefinite and are ordinarily considered to be mixtures containing both sulfonate and sulfate esters. We have found that practically all of these products can be used in the present invention, although there is some difference in effectiveness between mahoga'ny soaps of different petroleum companies. When noacid is used in treating the pulp, there is 'a very wide.difierence between mahogany soaps of'different' origins. It is a surprising effect of the present invention, however, that the acid treatment of the oreto a very great extent adjusts differences between mahogany-soaps of different origins. They all give improved results with acid and the difference between various ones is definitely lessened; This curiously different surface alteration of the iron ore and p l of the gangue. It seems reasonable to believe that the acid treatment may so alter the surfaceof iron mineral particles that good adherence is obtained with almost any mahoganysulfonate.

It is necessary to coat the mineral particles with the active mahogany soap. This makes it necessary to use some precautions in mixing the promoter with the ore. We have found that it :is de-. sira'ble to have the active ingredients in solution or dispersion in organic solvents. mahogany soaps are sold as an oil solution or dispersion of the sulfuric acid reaction products and, therefore, are already dispersed in a hydrocarbon solvent. These commercial products may be mixed with the ores directly or they may be further diluted with other organic solvents. The nature of the solvent does not appearto be critical. Excellent results are obtained with hydrocarbon solvents, such as petroleum hydrocarbons which are naturally present inthe commercial mahogany soaps, the latterbeing normally sold in the form of a solution in petroleum hydrocarbons. Glyoeride oils, of which cocoanut oil is a typical example, also give good results and it is possible to get good feeding with solutions in various alcohols and other organic materials. This leads usto believe that the main, if not only, function of the solvent is to effect more uniform distribution in the ore pulp, but it may also have other effects. because when it is attempted to feed the active constituents of themahogany soaps in the form ofv hot water dispersions the results are not as good. Therefore, it is preferred to introducethe collector in solution in an organic solvent without limiting the invention broadly to this preferred modification.

' The question of froth is present as in any froth flotation process, and various mahogany soaps show different frothing powers. Where adequate frothing can be obtained they may be used alone. However, in many cases it is desirable to use one or more frothers, for which the standard types of frothers such as pine oil, cresylic acid, mixtures of higher paraffin alcohols from 7 to '10 carbon atoms and synthetic frothers prepared from mixtures of these higher alcohols with hydrocarbons, may be used. We have also found that watersoluble reaction products of sulfuric acid with petroleum hydrocarbons from lubricating oil stock, the so-called green acids, may also be used as frothers and also show some promoting effect. When used alone with acid treatment, fair results are obtained. but not as good as with the mahogany soaps or acids of the present invention.

The technique of froth flotation is not materially changed by the use of the present invention, and this is an advantage because the operator does not have to learn new techniques, and standard flow-sheets and equipment may be used in most cases. Examples of typical flotation procedures are the use of the process of the present invention in rougher floats, cleaner floats, and the like.

*It is also possible to utilize the principles of the present invention in a. so-called doubleflotation process in which a rougher float is effected with the mahogany soaps or acids on acid treatedpulp, adjusting conditions for maximum recovery at some slight sacrifice of grade. The concentrate is then'treated with chemicals or agents to remove the collector from the surface of the. particles. ypical of such agents are. due.

bracho and other dispersing agents. The concentrate with collector removed is then subjected to a cleaning operation using a cationic flotation reagent to float out silica or siliceous gangue. This double float presents a more expensive procedure, but with some highly refractory ores it .is an economically attractive procedure.

1 It is an advantage of the present invention that itimay be used in such various manners so as to Commercial obtain the best results economically with various ores, taking into consideration the nature of the ore and the economic factors at the mines, such as availability of fuel, shipping costs and the like. In every case the present invention will be used to obtain the best economic results with any par ticular ore, and the wide latitude given tothe ore dressing engineer by the non-critical character of the present invention is of real advantage in permitting optimum results with a wide variety of iron ores. i

The problem of slime is not greatly different in the process of the present invention than in the general run of flotation processes. Here, as elsewhere, slime is never desirable. However, it is an advantage of the present invention that it is not peculiarly critical as far as slime is concerned and it is possible to operate with undeslimed ore or, which is more important, with ore which has been only partially deslimed, thus permitting more economical desliming procedures. The effect of slime is normal and manifests itself primarily in added consumption of reagent. As the reagents are fairly cheap it is sometimes desirable to use relatively economical desliming procedures which do not remove the slime completely and such procedures are permissible by reason of the relative lack of sensitivity of the present process to the presence of small amounts of slime. More involved desliming procedures, such as those employing a polishing or scrubbing of the ore particle followed by desliming, are not normally necessary although they may be used and do effect some economy of reagent. The extent to which the desliming is to be effected is largely one of economic compromise and the degree of desliming to produce optimum results with minimum costs will be determined in the case of each ore.

As has been pointed out above, the nature of the acid to be used in treating the ore is not critical, For most practical purposes sulfuric acid is preferred because of its cheapness. It is also one of the best acids. Other acids such as sulfurous acid, phosphoric acid and the like may also be used and in some cases, where waste gases containing S02 are available, they constitute a very cheap source of acid usable in the present invention. Within wide limits the purity of the acid does not seem to play any decisive result in the present invention, which'permits the use of lower purity acids which are sometimes available at considerably reduced prices and the possibility of using cheap material in the present invention constitutes a further economic advantage.

It is an advantage of the present invention that the addition of acid-"may take place at various points in the flotation procedure. Thus it may be added in the conditioner and in many cases this is preferable, or it may be used in desliming, or added directly to the flotation circuit. Obviously, of course, the acid may be added in portions at various points in the flotation operation. The fact that the acid addition is not critical permits a great deal of flexibility in setting up a flow sheet for any given iron ore.

Th Pr ent invention will be described in greater detail in conjunctionwiththefollowing specific examples, which are typical of the invention, and which have been chosen to illustrate certain of the ranges within which the invention gives good results. The parts are by weight.

Example 1 Minnesota iron ore having an iron content of about 30.5% Fe was deslimed and divided into a large number of portions. Some of these were conditioned at 22% solids with mahogany soaps from various sources and floated in a Fagergren flotation machine. Further tests were made in which the pulp temperature was raised to 50 C. and the mahogany soap fed directly to the flotation cell, these tests being made with and without additional sulfuric acid. Finally further amounts of the ore were treated by conditioning with the promoters and 5 lbs. per ton of sulfuric acid added to the flotation machine. In all tests the mahogany soaps werediluted with secondary butanol. The metallurgical results appear in the following table which is divided into three sections, the first section being the various mahogany soaps, the second, tests at higher temperature,

50 C., with and Without sulfuric acid, and the third, tests made with 5 lbs. per ton of sulfuric acid at normal temperature.

out above; better, results are obtainediby condi-- general no flotation took place. The reason for,

thepeculiar behavior of mahogany soaps with iron ore when contrasted with their action on other oxide'ores has not been determined, but is probably a surface phenomenon.

The amount of acid present in the treated ore pulp is sufficient to react with the major portion or all of the mahogany soaps to transform them partly or wholly into the corresponding free sulfonic acids. It ispossible to use the free sulfonic acids themselves and the results are substantially the same, but it is preferred to use the mahogany soaps, since they are not corrosive and do not present difficulties in shipping or handling Petroleum sulfonate used Concentrate Tailing Per cent Fe per cent Source Name Lbs/ton sg fi Fe assay Assay Dist.

Section 1 Standard Oil Company of California 2. 27 31. 28 44. 46.02 23. 70 Sonneborn Sons, Inc 2. 27 37. 57 48. 90 59. 97 19. 16 Atlantic Refining 00.... 2. 33 31. 52 49.10 50. 97 21. 74- Stanco Distrib., Inc. 2. 40 20.01 51.90 35.54 24. 95 D0 2. 66 28. 62 44.49 42. 59 24.05 Do 2. 40 43. 20 46.09 65. 77 18. 24 1:1 mixture of Oalol and SP-l 2. 20 32. 44.09 47. 51 23. 51 1 part of above mixture with 1 part of green acids (Sonneborn 40 32. 93 7. 98 50. 28 23. 30

Sons, Inc.) (water soluble). Sonneborn Sons 2. 67 2. 87 Atlantic Refining 00.... 2. 50 11. 31 Do 2.07 Penna. Oil Prod. Refng O0- 2. 13 0.92 Sherwood Refining Co Reagent 407 2.90 O. 83 Shell Oil C Crude naphtha sulfonlc soap. 1. 80

Section 2 1:1 mixture of Oalol and SP-l 2. 20 7.03 46.04 10. 60 29. 35 Do. 2. 20 31. 34 44. 34 46.14 23. 63 Shell Oil Co 1. 1.42 Do. 1.80 6. 77 12. 78 28. 33

Section 3 7 Standard Oil Co, of California C210] 2. 27 51. 39 34. 47 58. 53 25. 82 Sonneborn Sons Petronate. 2. 27 36. 15 48. 84 58. 51 19. 61 l 1 mixture of Calol and SP-L 2. 20 53. 98 39.74 71.17 18.88 Atlantic Refining Co.-. Ultranate #3 2. 30 55. 89 40.19 74. 12 17. 78 Sonneborn Sons O-Emulsifier. 2. 67 38. 23 52. 9B 68. 93 15. 71 Atlantic Refining Co--- Ultranate #l-.... 2. 50 42. 34 43. 97 61. 77 19. 98 Penna. Oil Prod. Reing Co... 2.13 28. 38 56.03 51. 20. 58

1 2% lbs. per ton of sulfuric acid added to the flotation. 2 No promotion. It will be noted that mahogany soaps or pep e 2 troleum sulfonates vary considerably in their promoting power. Some show no promotion at all and others, such as, for example, Petronate and 6 A further portion of the Minnesota iron ore used in Example 1 was deslimed and conditioned at high solids (about 67%) with 2 lbs. per ton of Ultranate No. 3, diluted to 22% solids and floated in a Fagergren flotation machine. In the first four tests the sulfonate was prepared as a 12% dispersion in hot water, boiled gently for 10 minutes and then fed to the conditioner, and in the next two tests the sulfonate was fed directly to the conditioner, in the next test in the form of adispersion in hot 3% sulfuric acid, and. in the last test as a dispersion in cold 3% sulfuric acid. I In some of the tests sulfuric acid was-added and in othersfuel oil.' The metallurgical results appear flotation alone is given, as the results of rougher in the following table. flotation are commercial.

- Lbs/ton Concentrate Tailing Sulfonate used Concentrate sul P Tailing ona e or per cent used, Fuel Per Per cent Fe cent Per Cent Per cent Fe Fe lbs/ton H2804 on cent Fe 1111 Name Lbs./ton wt assay Assay Dist. assay Assay Dist.

2.0 7.0 Petronate 3. 60 56.46 46.35 84. 70 5 go 2.5 43.10 54. 78 76.42 2.0 7.0 Ultranate #2 3. 49 56.82 49.61 91.93 2. 0 2. 5 45. 9e 5e. 49 85. 52 2. u 7. 0 SP-3l2 3. 25 4s. 30 53. s1 s4. 94 2. o 2. 5 s5. 45 60. 75 72. a5 2. 0 2. 5 Ultranate #1-- 3. 84 55. 07 47. I4 84. 33 2. 0 2. 5 37. 74 55. 3e 67. 91 Ultranate #s 2. 54. 9s 51-. 7e 95. 44 It H b t d th t h d t 1 1 t f 45.25 58.56 87.07

W1 e no e a w en no aci was presen 1111K We 0 c 1 1 dSP-L. 2. no flotation resulted. The addition of acid pro- 3 an 20 39 63 58 68 76 71 duced an excellent recovery of a material having 1 Allsulf ts 11'] t (1 'th 10 d t 1. a commercially acceptable grade. ThlS is quite 20 ma 0 In 9 W1 (Z'Wm My bu am remarkable as the concentrate is a rougher concentrate only, without any cleaning. The addition of fuel oil alone did not bring about any improvement, but gave good results when associated with sulfuric acid. It will be noted that excellent results were obtained in the last three tests regardless of whether the sulfonate and acid were fed directly or the sulfonate dispersed. in the acid.

Example 3 Concentrate Tailing Sulfonate Lbs/ton used, Per cent Fe lbs/ton H280 Per cent Per g PH Assay Dist. assay 2. 0 None 15. 10 52. 50 61. 48 5. 85 6. 9 2. 0 2. 5 20. 33 52. 86 83. 43 2. 68 2. 3 2. 0 2. 5 23. 40 52. 92. 90 l. 22 2. 5 2. 0 2. 5 24. 43 50. 43 96. 40 O. 61 2. 5

It will be noted that Petronate gives considerable beneficiation even without the presence of sulfuric acid, but the acid greatly increases the recovery. Under the best conditions with good dispersion the recovery is increased by about 50%. While the grade is slightly below commercial standard, which usually requires about 58% Fe, it is sufliciently high so that commercial results may be obtained by cleaning.

Example 4 The ore of Example 1 was used in a series of tests in which it was conditioned at high solids (67%) with various mahogany soaps, then diluted and floated using a rougher float and cleaner float. The amount of sulfuric acid was kept constant at 2 /2 lbs. .per ton. The metallurgical results appear in the following table in which the first line for the first 5 mahogany soaps represents rougher floats and the second line cleaner floats. In the .case of the last reagent, rougher Example 5 The effects of various acid concentrations were tested using the deslimed ore of Example 1 conditioned at high solids with 2.2 lbs. per ton of an equal mixture of Calol and SP-l diluted with 10% secondary butanol, followed by dilution to flotation density and flotation in a Fagergren flotation machine. The metallurgical results are as follows:

Rougher concentrate Tailing H 804, lbs/ton Percent Per cent Fe Per cent wt. Fe DH Assay Dist. assay None 9. 23 43. 13. 20 29. 28 7. 0 0. 50 46. 04 54. 05 81. 39 10. 54 5. 7 1. a0 42. 58. 32 82. 10 9. 57 3. 1 2. 50 39. 63 58. 68 76. 71 11. G9 2. 7

It will be noted that, as the amount of sulfuric acid increased, the results improved up to about 1 /2 lbs. per ton, reaching a maximum at about this point, with some loss in recovery when 2 /2 lbs. per ton of sulfuric acid was reached. With this reagent combination a pH of about 3 gives best results. It should be noted that in a single roughing operation, high recovery of a commercia1 grade of concentrate was obtained without any cleaning.

Example 6 Rougher concentrate Tailing f Per cent Fe assay, per 9? 0 Per cent cent Fe dimming Assay Dist.

Minutes 39. 63 58. 68 76. 71 11. 69 2 41. 32 59. 29 81. 77 9. 50 4 22. 22 59. 68 43. 31 22. 31 6 nsity hine.

tanol) together Temp. of p p Tailing Per cent Fe assay qual mixture of Calol and SP- Rougher concentrate, per

cent Fe A say Dist.

contained about 14.3% Fe with a quartz gangu was 'deslimed conditioned at" 65% solids with 2 Th lbs. per ton of an e (diluted with 10% secondary bu with 12.5 lbs. per ton of sulfuric acid. The conditioned pulp was then diluted to flotation de and floated in a Fagergren flotation mac The metallurgical results appear in the following table.

It will be noted that as the time of conditioning increases so does the recovery, but excessive conditioning brings about a drop. reason for this phenomenon is not known. However, the change is not sudden and the condi- 5 tioning time is, therefore, not critical.

Example 7 .This test was made to show the results obtain- 10 able with various types of iron ore. In every case the ores were deslimed, conditioned at high solids with an equal mixture of Calol and SP-1 (diluted with 10% secondary butanol) and optimum amounts of sulfuric acid. The conditioned pulp was then diluted to flotation density and with 10% secondary butanol) and 2.5 lbs. per ton of sulfuric acid wasefiected at various pulp-densi- 75 ties, followed by dilution to 227 solids and flota-v t e .f kw m o O 6083416 Sc S w e RE m s H 55 m 1 e n D. O n n 0.1 M .1m IL OQ COt a v t e .s .N m wwi m .m w v codename r em a sw p s 05200 F cew ....L.&2. u m. ed..P 136 a a e 30.30 a mw m wmi mmms r P r 1 at mmm mw nh d 4 4 HOTO r 0 eS .n 55212253 5 rmis c vd 62 2222 t 34505998 1 g d a m e .m a2 4M2 5 5 5 1 n h c 0 F D 7789887 1 t t e 4374. w w m .h p t 4793983208089406503 A bd a c sr t n. nd fiaeeddaaaaLatLzLzaa I r 94 742976 ou 1 g 6 2969 2124 .m. .m m M. 33132809 mm W W n Wu RM .568 829593839 l S f h a h amnnnmn Tt umf a m .m o m 56 t n. nedh 0 r un P. mmse a nt f a .m when m t c ct o n o v an 5 1 s m wmmdtts fir hct hsch m m.. nwnnnomw ma v mn m m s m ia c w n m t have n w men an? mn nm sm .v w m m 1 awnmuml P W nS m V H? t 62444 18733245396001 4434 t v a Yu n u a .a a, m .rmoeaoamaLaihaaauaaao r e. tl b t W t l 1222 1312 BI 323. m... mmmnewnm b ma m e 1 m n. r l r .w sr ue ea n e. e n e d e f w .e...v n m h w a e ttssntssscs H mm esm m e m T. v anamwwmnmmaamaammmw a r m r wmm F tra. I 07. .H ub.a 0 S. n 0 A5: m 4377395952293734344 2 m n 4 eaaaalazaeaeaeaeala a B m P e ev. a "hm e et tey W hmwmm a. twmw a m e T n o .1 I? a v h a e tc nnb ttttnctt fi d 3 m WWW S d V. wd m S Mm 5.5.5.5.555551L55551111 q q q 6 n r. e 1. 0 C .n manna a and w m e mmw in... t r. m an a a duT. e 1 H- a a a a r e T a I h;a%n m m mmm .mmm flmm m mslmfi. P m 0 P flfiww Ham 1 W 0 m m S n 6000060603060609080 mwmmm mm mmm .mo rmm s him. mm .m nm m m m m m m i a @NE NE mmmwmmmm mwm N .N N N N N N N 1 e O .rv 1 wnu I h m ne o r m mna ia w .m twm e mw o mm n f m sm m a mnns m e 0 e mmma a mm M Meie nm m n L 68105 .e m ss w n n T e MN tea m en Ma mud dm m 2a.. 1. m n umh bn .wnh ml MVMW m m h t ow b3 oacw n m u. mm 9 32323532 n m m am s w a Hb e p efia l ew W e0 6 n we bm Wh o a t m nmd nme s s dm m wa. HM 37639222 wmadh wm m n e n .mss CSVQm is wme m sub nmwmmnon Aem m 0 X. S 1 e b e .6 nmwmaw wnowwa n mT n 1 In absence of acid, froth was excessive, causing much mechanical overflow into the floatiproduets;

Example 9 j The effect of temperature was studied, using another low grade Minnesota ore. The ore, which 151 tion in a Fagergren flotation machine; The metallurgical results appear in the following table.

Concentrate per cent Fe Tallmg Pulp density j per cent solids incom Assay Dist. gggggg; r 3 dltmnmg The above tests show that optimum grade is obtained with. high solids conditioning. Conditioning at lower solids, while permitting excellent recoveries, decreases very markedly the degree of concentration.

Example 11 Concentrate Tailing Pulp density per cent Per cent Per cent solids in Fe Dist. Fe pH flotation assay assay The variation of flotation pulp density causes a considerable change in grade, the best results being at the very low density of, 11%. At this density, however, v the capacity of the machine .is

decreased and the particular density tobe chosen tween output and gr'ade V V fEmampZe '12 i I slime. was determined, using a low will be the result of an economic" compromise be The effect or into three'portions, ,the first of which: "was desliined thoroughly, the Ssecond was not 'deslimed at all; and'the-third was'partially deslimed. Conditi'oning was efi'ected at high solids with the 12 It will be apparent that deslimingis helpful, although the presence of slime does not preclude obtaining fair results but at a higher cost for reagents.

Example 1 3.

The efiect of various. acids was determinedaby testing with a low grade ore such as that described in Example '12. Inevery case the ore was conditioned at high solids with 2.2 lbs. per ton of an equal mixture of Calol and SP-l diluted with secondary *butanol. Rougher flotation only was conducted. The metallurgicalresults are shown in the following table.

15 Acid used I Concentrate Telling Per Per cent Fe Assay Type Lbs/ton ceni:1t 7 per cent pH 7 weig Assay Dist. Fe.

N'oue control test. 13. 87 52. 98 58. 60 6. 03 6. 8 Hydrochloric 2. 5 24'. 39 46. 04 91. 72 l. 34 2. 7 Nltric 2. 5 26. 74 44. O9 92. 31 1; 34 2. 7 Hydrofluoric- 48 3. 54 22. 52 51. 89 91. 18 1. 46 2. 8 25 Hy d r oilucrsilic- 10.(27%30%) 3. 99 23. 01 50. 91 92. 23 1. 22 2. 5 Boric 2. 5 14. 17 54. 20 62. 45 5.38 6. S Perchloric 2. 5 26. 57 43. 20 89. 72 1. 79 2. 7 Phosphoric 2. 5 21.12 52. 69 88. 74 l. 79 2. 7 Sulfllrous 2. 5 19. 93 55. 77 90.02 1. 54 2. 3 Carbonic 25. 50 43. 92 89. 74 1. 72 6. l

1 Saturated.

for economical operations on a-commercial scale.

In generai, a dissociation constant between 10- and 10- represents the lower limit of utility.

Example 14 4 Various dispersing agents can be used in the present process prior to desliming. "The following tests; were made. The ore used was that of Example '1 and the dispersing agents were added prior to deslirriing. III-each case conditioning was effected at high solids'with 2.2 lbs. of the grade Minnesota iron ore. This ore was divided secondary butanol mixture of Calol and SP-l and 2.5 lbs. per ton ofsulfuric acid (except in the case of sodium hydroxide, where 3.5 pounds of sulfuric acid per ton were used in order to neutralize the alkalinity). Thepulp was diluted to secondary butanol mixture of Calol and SP-l and sulfuric acid, the optimum amounts oi reagent and acid being used in each case. The metallurgical results appear in the following table.

cent Product P .P gisttri' er or n 1011 cent cent Fe '22" HiSO Fe insol.

Substantially complete desliming:

Calc. head 14. 53 Slime 40. 92 Clean. cone 60.17 2.50 Clean. tail..- 11.57. Rough. taiL. 0.85 Rough. cone. 53. 49. N o desliming: l Calc. head 14.55

Como. No 41.53 Clean. conc No 55.115 Clean. ta 15.47 Rough. tail 4. ()2 Rough. cone. No. 2... 36.61. Partial deslimingz- Gale. 1; -14. 22.

Slime- 35.93 Rough. con 56.52 i

' Tallinn" flotation density, and floated in a Fagergren flo- "tation machine with a single cleaning. The following metallurgical results were obtained.

55 V Additionalreagents h Concentrate Tailing Per cent Fe per cent 'Percent Fe Name Lbs/ton wt assay Assay Dist.

sodium silicate 3.00 42. 5e 60. 25 84.35 5.26 Sodium dioctyl s los ll'ccinatenfl 0. 50 37. 77 61. 41 '68. 71 11. 54 Sodiuin hydroxide. 2. 00' 42.14 60.77 85.05 s13 Calcium lignin sul-- 6-5 fonate (crude). 2.00 39. 97 61. 41 81. 26 6. 67

Itwill be noted that the use of the dispersingexit invention as it permits the use of agents which aid in desliming.

Example 15 Anumber of tests were runwith the deslimed ore of Example 1 to determine the effects'oi varyfirst four tests used a constant amount of re.

agent, 2.2 lbs. per ton of an equal mixture; of

Calol and SP1, diluted with secondary butanol, and the second four tests used a constant amount of fuel oil, 1.12 lbs. per ton,'and

varying amounts of the alcoholic mixture of Calol and SP-l. The metallurgical results are shown in the following table.

Lbs/ton Concentrate 1 Tailing Sulfonate used, Per cent Fe i gz lbs/ton Sulfuric Fuel Per cent 9 acid oil weight Assay Dist.

2. 20 y 2. 50 None 45. 38 56.52 84. 26 8. 77 2. 20 2. 50 0. 56 47. 32 56. 88 89. 54 5. 97 2. 20 2.50 1.12 47.09 58.83 90.07 5.77 r I 2. 20 V 2.50 2. 24 32. 50 v 58. 83 62. 79 16. 79 7' 1. 65 2. 50 1. 12 28. 34 57. 82 53. 98 19. 49 2. 20 2. 50 1.12 47. 09 58.83 90. 07 5. 77 2. 75 2. 50 1. 12 50. 09 57. 31 94. 53 3. 33 3. 30 2. 50 1. 12 51. 94 56. 44 96. 60 2. 15 After one c eaning operation 48. 58 59. 61 95. 42

It" will be noted that there is an optimum amount of'fuel oil and an optimum'amount of reagent. These amounts will varysomewhat from ore to ore and from reagent to reagent.

'''The following tests were made to compare various organic solvents and materials'used in combination with mahogany-soap. Theore and conditioning procedure was the same as in the preceding example. In each case 2.2 lbs. per ton of an equal mixture of Calol and SP-l; diluted with 10% secondary butanol, and 2.5 lbs. per ton of sulfuric acid were used in the conditioning step, at which time the additional reagent was also introduced. After dilution to flotation density the pulp was floated in a Fagergren flota- It will be apparent that the present invention is not at all critical with respectto the organic solvent used, commercially acceptable results both from the standpoint of grade and recovery being obtained in each case.

" Example 1'7 A further series of tests was made on the ore used in Example 16, but a different" petroleum sulfonate, namely Ultranate No. 3, was employed. In each case the reagent consisted of 3 parts'of Ultranate No. 3 to 1 part of the organic solvent. The amount of sulfuric acid used was 2.5 lbs. per ton as in the preceding example. A rougher con-J centrate only was taken. The metallurgical results appear in the following table.

The use of acid salts instead of acids'wa's illuse trated by the following testsin which a deslimed ore similar to that in Examplel was used, being conditioned at high solids with varying, amounts of the'secondary'butanol mixture of Calol and SP-l and acid salts. After dilution toflotation density in the first test a roughing float followed by a single cleaning was used and in the second test a rougher concentrate only was'taken. The metallurgical results appear in the following table.

Acid salt a Concentrate Tailing' Sulfogate P t F use 5 Per er cen e Assay lbs'lton 7 Name Lbs/ton cent per cent I pH Assay Dist. Fe

4. 40 Potassium blsulfate 10.0 44.00 60. 96 88. 64 4. 89 2. 4 2.20 Sodium chlorosulfonate 6. 0 42. 78 59. 28 83. 12 9. 00 2. 4

tion machine and cleaned fence. The metallurgical results appear in the following table.

' 2 Example 19 V Additional reagent Concentrate Tailing assay Per cent Fe per cent Name Lbs/ton cent Fe 7 wt Assay Dist.

Oleic acid. 0.75 49.81 57.82 94. 12 2. 69 Talloelu'fl j 0. 75 51. 10 57. 05 95. 09 r 2. 44 Naphthenlc acid. 0. 68 43. 39 59.36 84. 30. 6. 79 Cottonseed oi1 0.70 45. 09 60. 25 88. 42 3. 72 0. 42. 49 60. 25 83. 35 6. l5 0. 68 47. 53 58. 97 92. 65 2. 31 0.67 42. 57 60.38 83. 15 6. 28 1. 00 35.41 59. 87' 69. 61 11. 15 0. 74 45. 72 60. 90 90.15 3. 85 0.83 39. 26 ,59. 23 75. 77 10. 26 Chlorinated kerosene-.- 0. 53 45.01 59. 74 87. 47 3.- 33 Fuel oil No; 2 1.12 47. 09; 5s. 83: 90.07 7, 5. 77

Bougherrllotationonlym The double flotation of Minnesota iron ore conluted, subjected to flotation, conditioned with additional 1.1 lbs. per ton of the sulfonate. mixture and again floated, followed by treatment of the concentrate with quebracho and soda ash and desliming. Cationic flotation with pine oil and 75 laurylaminehydrochloride was then conductedLE The flotation procedure and metallurgical results are tabulated in the following table.

tion because it permits obtaining good results with many iron ores in a flotationcircuit which is sub- Laurylamine Elotationanionic. Condition the cone.. Deslime lilotation-cationic Percent Assay per Dist. per

Pmduct wt. cent Fe cent "Fe Head.. 100.00 28.98 100.00 Primary slime 5. 14 22. 89 4. 06 Rougher tailing 39. 70 2. 57 3. 52 Secondary slime. 4. 06 15. 69 2. Silica conc 4, 45 24. 18 3. 71 Iron tailing" 46. 65 53. 75 86. 51

Example 20 flotation machine to produce a rougher'concen- I trate and, following the addition of more sulfonate a scavenger concentrate, the scavenger concentrate being intended to be treated as a middling and recycled in the circuit. The metallurgical results appear in the following table inwhich the scavenger concentrate app ars in the second linev of eachsuccessful test.

Concentrate Final tailing 'Per cent Fe Sulfonate Sulfuric Soda ash"; used, acid, lbs mm lbs/ton lbs/ton Assay,

Assay Dist. per cent pH 2.20 2. 5 None 58. 68 76.71 1. 10 None 39. 28 15.1)6 5.12 2. 6 2.20 None 5. 0 No useful float V 10.0

produced 2. 20. 2-5 3.0 57.43. 79. 49 1. 10 Noll 27. 69 13. 05 5. 26 6.8 2:20 2:5 4. 0' 59. 10' -65. 95' a 1. 10 None 39. 49 23. 21 6. 92 7. 3

The results clearly show that, in the absence of acid, soda ash prevents any useful float, whereas if the ore has been treated with acid, a considerable amount of soda ash, :up to :the, amoun which results in an almost neutral. circuit,-does not adversely afiect the recovery and grade. When the amount of soda ash is increased still further some falling ofi in recovery is to-be noted; but in this case the gradeof the scavenger concentrate is much higher and, therefore, ;a cone, siderable portion of the iron values would :be recoverable therefromj This results in an overall iron recovery when recyclingiof the middlings is employed, which is not substantially "poorer than with' smaller amounts of soda ash. The reason.- forthe curious behaviour of acid-treated ore is not known, but it indicates that the pH. oithe flotation circuit is not thefcoiitrolling factor;

stantially neutral, and, therefore, does not present a serious corrosion problem, making it unnecessary to use acid-proof material except in the conditioner which is a type of apparatus more readily acid-proofed than flotation machines. Any of the ordinary alkalies, such as caustic soda or ammonia, may be used. Alkalies which form insoluble compounds, such aslime, ,do not ive quite as good results. Because of its relatively lowcost and excellent results, soda ash is normally preferred.

In the examples the invention has been described in connection with the use of a Fagergren flotation machine. This machine gives excellent results in the process of the present invention and is preferred. However, theprocess of the present invention is in no sense limited to any particular flotation machine and any of the ordinary types of flotation machines may be employed. All of, the oil soluble petroleum sulfonates referred to in the examples under the trade names are typicalpetroleum sulionates of the mahogany soap or acid type as commercially obtained from the treatment of .petroleum lubricating oil fractions with sulfonating: agents, such as sulfuric acid, oleum and .the like.

We claim:

1. A method of vbeneficiating oxidized iron ores by froth flotation of the cm in the form of an aqueous pulp, which comprises conditioning the or with an inorganic acid substance, the anion not which is a constituent of an inorganic acid having a dissociation constant of at least 10-", the

amount of said acid substance being such that on dilution to froth flotation density and floating. the rougher tailing in the absence of added alkali shows a pH in the range of 2 to 6, and subjecting the-aqueous pulp of said treated ore to froth flota- This is an added advantage of the present invention in the presence of a collector for oxidized iron minerals, the major constituent of which is an oil soluble petroleum sulfonate obtained in the refining of petroleum lubricating oils and removing a. concentrate relatively rich in iron and a tailing. relatively'poor in iron. 7 j

2. Amethod' of b'eneficiating oxidized 'iron ores by froth flotation of the ore 'in'the form of an aqueous pulp, which comprises conditioning the ore with sulfuric'acid, the amount of said sulfuric acid being such: that ondilution to froth flotation density and floating, the rougher tailing in the absence of added alkali shows a pH in the range of 2 to 6, and subjecting the aqueous pulp of said treated ore togfroth flotation in the presenceot a collector :foroxidized iron minerals, the major'constituentof which is an'oil soluble petroleumsulfonate 1 obtained in the refining of petroleum lubricating :oils and removingv a concentraterelativelyrich in iron and atailing relati-vely poorvin iron. Y 3. A method according to claim 1 in which conditioning is effected at high solids with bothcollector and acid substance and the thus condi- 17 tioned pulp is then diluted to flotation density before froth flotation.

4. A method according to claim 2 in which conditioning is effected at high solids with both collector and sulfuric acid and the thus conditioned pulp is then diluted to flotation density;

before froth flotation.

5. A method according to claim 1 in which the conditioning is with a mixture of petroleum sulfonate and an unsulfonated oil.

6. A method according to claim 2 in which a 18 the conditioning is with a mixture of petroleum sulfonate and an unsulfonated oil.

7. A method according to claim 1 in which the conditioning is at high solids with the acid substance, petroleum sulfonate and unsulfonated oil.

8. A method according to claim 2 in which the conditioning is at high solids with sulfuric acid, petroleum sulfonate and unsulfonated oil.

ROBERT BEN BOOTH. EARL CONRAD HERKENHOFF'. 

